A Wireless Local Loop (WLL) network utilizes wireless techniques to provide terminal services for fixed terminal devices or local mobile devices. In the case that wireless access is provided by Code Division Multiple Access (CDMA) WLL, the function of wireless local private branch exchange can be implemented by a fixed wireless station to be connected to a Private Branch eXchange (PBX), and a wireless PBX network is formed. The PBX may communicate with one or more fixed wireless stations, and for the CDMA WLL, it means that the PBX communicates with one or more fixed wireless station users. The PBX is connected via a telephone interface to the fixed wireless station directly, and the fixed wireless station accesses a Public Switched Telephone Network (PSTN) via a Base Transceiver Station (BTS) and a Radio Access Controller (RAC). In this way, a plurality of wireless links may be established between the PBX and the PSTN. By enabling a plurality of users to share one or more fixed wireless stations, such a networking approach may effectively reduce the cost and meet a demand of corporate users and users in mountain villages, islands, or fishing ports for basic telephone service. However, because the users within the service scope of the PBX may call each other without passing through the PSTN, billing for the calls between those users within the service scope of the PBX may not be carried out.
During the process of making the present invention, the inventor found that a billing system is disclosed in Chinese Patent No. 97108975.2 titled “Billing Method for Wireless Multi-User Unit,” in which an additional air interface billing signaling is added between a PBX and a base station, so that the billing ticket generated by internal switching and stored in the PBX may be transmitted to the billing system at the PSTN side. In this solution, the billing information is reported by means of a private billing signaling and, therefore, software of the PBX, a fixed station, a base station system, and an exchange has to be modified appropriately, which is a quite difficult job. In addition, because the processing of a large amount of billing signaling will increase the signaling load for respective devices, the traffic is so limited that there is a possibility of signaling loss, and because an end-to-end confirmation mechanism is unavailable, it is impossible to ensure reliability.
A billing method is disclosed in Chinese Patent No. 99116281.1, titled “Method for Communication of Multi-User Fixed Wireless Terminal,” in which a billing module is arranged inside the PBX, the billing module generates a billing ticket according to a call or a release, and then transmits the billing ticket to the fixed wireless station communicating with the billing module. When the fixed wireless station detects the billing ticket, it sends the billing ticket to a fixed wireless terminal communicating with a billing center, and then the billing ticket is transmitted to the billing center by the fixed wireless terminal. However, in this solution, the billing center collects the billing information from respective PBXs by connecting to a fixed wireless terminal. Therefore, an interface to the fixed wireless terminal has to be added in the billing center. However, the fixed wireless terminal communicating with the billing center may not deal with heavy billing information traffic. Furthermore, because the billing ticket is reported immediately when the call is switched on and released, more and more calls will result in busier and busier billing ticket reporting, which will degrade the system performance and reduce the air interface resources available for normal calls.